The protection of crops from weeds and other vegetation which inhibit crop growth is a constantly recurring problem in agriculture. To help combat this problem researchers in the field of synthetic chemistry have produced an extensive variety of chemicals and chemical formulations effective in the control of such unwanted growth. Chemical herbicides of many types have been disclosed in the literature and a large number are in commercial use.
Unfortunately, many of such herbicides will exhibit phytotoxicity to the desired crop as well as to the weeds sought to be controlled. Thus, there is a long-standing need for selective herbicides which will control frequently occurring weeds but which will not adversely affect the crop plants when applied at herbicidally effective levels.
U.S. Pat. 5,006,158 to Carter et al. discloses 2'-nitro-substituted benzoyl cyclohexanediones having the structure: ##STR1## wherein R.sup.1 and R.sup.3 --R.sup.6 are hydrogen or alkyl, R.sup.2 is hydrogen, alkyl or alkoxycarbonyl; R.sup.7 is hydrogen or alkoxy; and R.sup.8 is hydrogen, halogen, alkoxy, alkyl. OCF.sub.3, cyano, nitro, haloalkyl, optionally substituted amino, optionally substituted aminosulfonyl, alkylcarbonyl, alkoxycarbonyl or R.sup.6 S(O).sub.n wherein n is 0,1 or 2 and R.sup.6 is substituted alkyl, phenyl or benzyl. Specifically disclosed, as Compound 8D, is 2-(2'- nitro-4'-trifluoromethylbenzoyl)-1,3-cyclohexanedione. Such compound is demonstrated to be an effective preemergence herbicide against a wide variety of grasses, broadleaf weeds and sedges when applied at a rate of 2.24 kg/ha.
It has now been discovered that such compound will effectively control a broad range of weeds typically associated with corn without exhibiting any substantial phytotoxic effect on the corn itself.